1. Field
The present disclosure relates to the field of communications, and in particular to a bit allocation method and apparatus for a multicarrier modulation signal, and a system.
2. Description of the Related Art
Multicarrier modulation employs multiple subcarrier signals. It decomposes a data stream into several sub-data streams, so that the sub-data stream has a much lower transmission rate, and these data are respectively used to modulate several subcarriers. A multicarrier modulation signal features in that transmission rate of the subcarrier data is relatively low and the periods of code elements are relatively long, etc. The multicarrier modulation may be achieved by multiple technical means, such as discrete multi-tone (DMT), and orthogonal frequency division multiplexing (OFDM), etc. Fast Fourier transform (FFT) is an effective method for achieving the multicarrier modulation.
A problem exists in a multicarrier modulation signal is that its peak to average power ratio (PAPR) is relatively high. In practical applications, a peak value of an output signal of a transmitter is usually limited. Hence, in order to increase average power of a signal, a PAPR of the signal needs to be lowered. One of the most frequently used methods is to directly perform clipping on the multicarrier modulation signal. The clipping method introduces signal distortion while lowering the PAPR and increasing the average power of the signal. And on the other hand, as a multicarrier modulation signal is formed by superimposing multiple subcarrier signals, in some special bit patterns, an extremely high PAPR will occur, and performing clipping on symbols of the extremely high PAPRs will produce large signal distortion, resulting in occurrence of a burst error in the symbols. Although a probability of occurrence of such a burst error is not high, which has quite small effect on the average bit error rate, such a burst error will cause invalidation of decoding of forward error correction (FEC), thereby resulting in communication failure.
It should be noted that the above description of the background art is merely provided for clear and complete explanation of the present disclosure and for easy understanding by those skilled in the art. And it should not be understood that the above technical solution is known to those skilled in the art as it is described in the background of the present disclosure.